Elongated leaves and pale green color on cactus and succulent

Hi everyone,
I purchased these plants about a month ago and placed them both in my room where the light is fairly brigth in the mornings. Initially they were dark green and had short, plump leaves. The succulent lived on my bookshelves and the cactus was was on my desk right in front of the window where it gets a few hours of direct sunlight on a sunny day. It's flowers only open on the side that faces the window and only when the sun is very strong. Now the leaves on the succulent have elongated, I can actually see the deformation as they become longer, thinner and lighter green at the base as compared to the top which is the old part of the plant. The cactus leaves have become rarer, thinner and turned light green. Why does this happen? Too much light or too little light? This is the brightest room in my house - should I place them outside in direct light? Or get a UV lamp? Thanks for your help!
Diana

 

Too little light. This is known as "etioliation", and is the result of low light in combination with high night temperatures and too much water (in relation to the other variables). They can be kept outside in summer, at least in the southern part of Canada, but note that they can easily be scorched if suddenly exposed to direct, unfiltered, sunlight, especially the light green areas. They should be gradually introduced to UV light, very much like humans. The sensitivity to UV light varies, some species are far more tolerant than others and can be put directly in full sunlight, others get damaged after a few minutes. Your cactus is a Mammillaria decipiens, I think, and it should be moderately easy to adapt to outside conditions. Perhaps 15 minutes of direct sunlight the first day, then put it in the shade. Increase exposure over the next 2 weeks. The other one is probably a Haworthia, a genus that I don't know much about, but I would try a similar treatment unless I find more specific information about that genus.

 

Thank you for the detailed response. Here they are now, sunbathing for 15 min. Leaving them outside at night will allow them temperatures of below 10 C as it is still fairly cold. Thank you for identifying the plants. Enjoy the weekend!