Looks like they are not getting enough nutrients because the lower leaves are yellow, and the top leaves are still green, which is indicative of Nitrogen Deficiency.
The top leaves are stealing all of the nitrogen from the bottom leaves to stay alive, and maintain growth, but they are fading fast.
The soil might also be dry from all the heat.
The soil looks super dry to me. I would water the hell out of them until there is like 30% run off coming out the bottom of the pots, and spray the leaves, every 3 days, or every 2 days if it starts getting big and thirsty
I would flush the hell out of them with SuperThrive, and Alaskan Fish Fertilizer. I would go buy it as soon as Lowe's or Home Depot opens...
Lowes is more likely to carry SuperThrive, and Alaskan Fish Fertilizer, while Home Depot usually only carries Alaskan Fish Fertilizer.
I would also give them some SuperThrive. SuperThrive has root stimulators as well as 50 different kinds of plant growth hormones. I only use it to germinate, and when they are seedlings once or twice. Never use it near the Flowering stage, or the plant could change into a male.
https://www.lowes.com/pd/SUPERthrive-4-fl-oz-All-Purpose-Food/1000057545
SuperThrive description: Enables plant success when over-wet, over-dry, over-dark, over-light, over-hot, over-cold, over-saturated with sea water or sea winds, over-buffeted by wind or people. Heals open plant wounds to aid in preventing fungus invasion; fluorescent plants to aid in reducing attraction to some pests. Speeds germinating and development of seeds, cuttings, bulbs and plants. May save years of waiting for harvest ability of fruits and nuts. Improves fruiting and vegetables. Uses up constructively excess fertilizer. Improved root system reaches maximal soil fertility.
And Alaskan Fish Fertilizer, which won't burn, and is safe for seedlings. All organic with an NPK of 10-1-1. I would still try to use half strength tho.
https://www.lowes.com/pd/Alaska-Fish-Fertilizer-1-Quart-Natural-All-Purpose-Food/3083645
Alaskan Fish Fertilizer description: Nutrient rich fish has been used as a fertilizer for centuries. The pilgrims knew to bury fish in the soil to assure vigorous plant growth and plentiful harvests. Generations of gardeners have relied on Alaska Fish to give them all the benefits of this traditional, time tested fertilizer in formulas that are easy and convenient to use. Alaska Fish offers pure fish organic fertilizers in formulas that gardeners want. Alaska Fish fertilizer can be applied using a sprinkling can or clog free hose end garden feeder. This product is for use in organic gardening. Use on all indoor and outdoor plants. It is all purpose deodorized fish emulsion fertilizer that is derived from seagoing fish.