Hi Ked.
I would definitely drink plenty of water. Remember when photoreading that is a lot of activity for the brain so you definitely want to drink plenty of water and stay hydrated.
Check up on your relaxation techniques. It is important to be in the relaxed, accelerated learning state.
Make sure you are taking plenty of breaks. 5 minute breaks every 20 to 30 minutes.
And last sleep. Are you getting enough sleep? Too often many people are not getting enough sleep and are sleep deprived. That will definitely create problems. Also if you are not getting enough sleep you will need more than just one night's good sleep to catch up. It could take days depending on how long you have been sleep deprived.
Photoread4me