I disagree about the whole hay issue. I already posted a reply to your other post regarding hay. I don't know ANYONE who feeds free choice hay and very few who feed ANY hay at all. Market goats don't live long enough to have to worry about their rumens developing. I give mine a HANDFUL maybe once or twice a week more as a treat than anything. My kids are 4th generation in 4-H and we have NEVER fed our market goats hay. Every one of my kids' market goats has made weight and won their classes. Whoever told you not to feed hay knows what they're talking about. You don't want big rumens on market goats.
If it is too warm they will tend to eat less as well. They're like people. I know I don't feel like eating when it's hot. Keep them cool. If you don't have them in a barn with lights you can try putting up a light by their pen. As long as it's light they will eat. This helps if it's hot during the day because then they will eat during the night when it's cooler. Lots of exercise also builds their appetite. Make sure you feed them at the EXACT same time everyday and do it 12 hours apart. We've had a few that were just brats about not wanting to eat the show feed. Put a scoop in their pan and give them 15 minutes to finish it. If it's not finished empty the pan and wait until the next feeding. They WILL get hungry and they will learn very quickly that they have 15 minutes to eat and if they don't then they go hungry. Once they get to where they empty the pan in the 15 minutes then up the amount of feed. Give them 15 minutes with the new amount and dump whatever is left after that time. Keep going with that routine until you are up to about a pound and a half of feed per feeding. Anything over 3 pounds of show feed a day is a waste and is doing nothing for the goat.
Just a couple of tips for you to try
It's going to be close as far as your weight goals as a goat can only gain so many pounds a month. Good luck!