Only hose I see, is aftermarket replacement upper rad hose. So I've to little to go on.
"White" could be acid, salt or aftermarket coolant or combination of. Combined with, heat and dry plastic.
When radiator level low, even a little. Air pockets accumulates in the top of it and in heater tees. The plastic, then, prematurely dries out. As your plastic is. So, you for sure have signs, of running engine low on coolant long term. How low for how long, I can't says. Other than to say for many many heating & cooling cycles, over a period of years. If a few inches low, where it was still above top of radiator fins. It just ran hot. If much lower, where below tops of fins. It may have overheated.
Note: Water temp gauge, will read below normal op temp. Normal is center (3 o'clock) line or slightly above, when coolant level low. Since, water temp sensors, ends up in air pocket, rather than liquid.
The way to check coolant level and get air out.
After bring engine up to operating temp and above 2,500 RPM for 5 minutes (HWY drive best). Park on level ground or better yet. With front of vehicle higher than rear. In either event, cross level also. Check under radiator cap before sun up, after 5 to 8 hour cool down. Top coolant with Toyota SSL (Pink), to very top. Top resevoir to high line. If need to add coolant today, check again next day. Repeat until no more coolant can be added.
Watch fuel trims (FT) and engine coolant temp (ECT), while driving. There are many OBD device on the market. That wireless connect to your smartphone. I use OBDIImx for iphone, to get most date points (PID). I can get FT, ECT, AT temps, AHC Mpa, CAT temps and a ton of other PIDs, my BlueDriver OBD device can't. But BlueDriver seems more accurate on fuel trims. These OBDII devices read DTC (codes) and also log in the background, entire time they on. A very worthwhile investment, even if you don't wrench
Study for signs of over heating:
Get pictures of all rubber hoses, vacuum & water. Study for swelling, discoloration, harness and cracking.
Examine, ever inch of head gasket. Use a flashlight from below looking up along block to head gasket. For the head gaskets inner area, in valley under VVTi intake manifold. You'll need a borescope to study head gasket.
Watch for smoke with a sweet smell, especially on cold start-up. (not to be confused with conidiation/vapor)
If you see, signs of head gasket leak or just want to dig deeper:
When replacing spark plugs. Study plugs, for steam cleaning.
Use borescope to study inside cylinders on piston tops & head chamber for steam cleaning.
Pressurize coolant system to ~15PSI, while engine cool. Use a borescope to study head gasket from within cylinders, for drips of coolant.
Do a compression test.
Look at my Master Thread which you'll find a link to in signature line. You mat find some help threads within it. First study the alerts at top of page.
Since you the VVTi engine and I see sign this vehicle from humid, hot and likely salt air climate. Your S.A.I. filter has likely already failed. So for sure study my S.A.I. filter mod, under alerts. I use a borescope, with 6mm direction camera lens, to inspect this filter. One may be able to see, with the more common,8mm directional (IDK).
