What are the temps and humidity? That one red light does not look like it would be enough for heating. Also, it's better or more preferred to use a CHE for night time heat so it can be dark like it would naturally be. Also, wet and cold makes a sick tortoise. Hot and humid does not. Rf need a high humidity. I don't know if YF do.
I had the red light hanging inside the tank and it was at 100 , thought that was to hot? the cooler end is at 73 , overnight with both lights off it stays at 70. And under the red light it's 85.
I don't keep RF tortoises (well, I do have a couple that I'm babysitting), so you can take my suggestion or leave it.
I've read here on the Forum, that the temperatures inside a RF tortoise's enclosure should be an overall 80F. From what I've read, you don't have to have a gradient from cool to hot in the habitat for RF tortoises.
Are you aware that we have a very nice group of articles on RF tortoises in the Tortoise Library