Need some advice on alfalfa for guinea pigs?

 
Need some advice on alfalfa for guinea pigs?
OK,I have two guinea pigs,and was wondering is they are eating too much alfalfa. It is supplied all over their cage.i have a little rack on the upper level,a big house which they love (pictured below), and little tubes and boxes filled with placed randomly.am i feeding them too much? Please no stupid comments and other advice would be appreciated. Thanks and GOD BLESS!!

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