Smart pots , air pots root problem

Hello i am growing 4 plants in coco handfeeding them . i am using 15 ltr air pots or smart pots whatever you call them http://www.1-hydroponics.co.uk/miscellaneous/airpots.html . i am currently in week 5 of flowering and noticed roots coming out of the bottom of the pot . is this a big problem or is it normal ? i have the pots sitting in individual trays , do i water the plants as normal or can i pour abit of water into the trays aswell so they can drink it up from the bottom . please reply thankyou i dont want to screw things up at this stage .
i am growing 2 sensi seeds big bud and 2 advanced seeds critical , the plants are looking lovely with nice buds

please help me with my question thankyou

no do not water the bottom of the tray tho, water normally from the top on your coco, and then let dry, and water again. every few days or however you do it (at least for soil) mr drywall is right, the root pots or smart pots, they will air prune, but you must have the pot in a coaster or solid surface.. a friend had some on the ground and the roots just wanted to stretch down to the ground since they were touch the ground.. after last years outdoor harvest we emptied out a lot of wasted soil, and big spun around roots at the bottoms of the smart pots.. instead of being all thu the bag, the roots were trying to stretch into the ground.. so if you're indoors, i'n sure you're good.. hope all goes well, peace!

I just finish a grow(14 plants) with those pots and I had some with very long roots underneath and never worried about and got great results.was indoor on cement