Red plants do tend to be of the higher demanding variety. Meaning Co2, high lights and ferts are the usual requirement to make them grow lovely and red.
If the tank set up is lower than what the plants demands then soemtimes the growth is slow or not at all, and sometimes the red leaves will revery back to green. Depends on the plants really.
So it may be worth asking if you already have a high tech tank set up or a standard or low tech set up otherwise you may lose these plants thus time, effort and money potentially will be wasted.
A little research and homework is always advisable if youre ever unsure on anything in this hobby.