At 83F, your lights-on temp is a little high. Leaves curl upward to transpire when air temp is high. It looks like the leaf ends are curling upward; am I seeing that right? Your pH is interesting in that it is higher on the way out than going in. Should be the other way around, but at any rate, it's not bad at all. I wouldn't mess with it right now. Also I don't know if foliar feed is what you want to do, although it doesn't appear to have a bad effect as your plant looks good. 0.2 of phosphorus may not be enough to go through flower, although if fed directly to the leaves it might be ok provided you don't over do it. Info I found on Plagron Growmix is that its fert content is good for the the first 3 weeks of veg, which is probably the typical duration of veg for most indoor grows. You'll have to consider using a blooming fert. Plagron has a couple ferts, one called Terra Bloom, that will work great if the NPK adequate. As always, read the lables. Try to get the most for your money. If Terra looks like it has most or all the micronutes and good NPK, then it should work great in that soil. Actually a 5 gallon pot is enough to get through flowering, if you do this right. The biggest problem for adding ferts after the plant is in soil is that it's hard to tell how much to give and how often. Alot of people overdo the fert because they don't know what's still available in the soil and what isn't. Probably the best way to handle this is to wait until the lower leaves become pale green to maybe a little yellow, then give a fert dose. The directions on the container will probably tell you how much fert to use per liter or gallon of water. Also, you want the soil to dry out some before watering, to let oxygen get to the roots. Your watering amount might be ok at temps in the low 80's, but you don't want to overwater. I think your plant looks pretty good, actually. best of luck.