Baja mentions it being lankier due to the lack of lighter indoor, which I would agree, but....
This may be written like advice, but first it is a question.
Can this be avoided? I have not grown this Euphorbia, but my experience with this genus, is telling me the looks dense. Even though, it has lots of perlite, it appears to have compost or soil as it's base.
Plants get more wobbly because their tops have outgrown the roots. Compacted soil will cause this. Adding more coarser grit in the future. I use a blend of 80% aggregate and 20% bark with nothing else. The bark may not be needed, but I do that to increase the diversity of microbes in my grow mix. I use a size materials no smaller than 1/8th, but not larger than 1/4", but pick one size and sift for that size. In a hot dry location maybe 1/8". All the aggregate is 1/8". For bark I use a sieve that has slits 1/2" long, but only 1/8" wide.
The second part is excess nutrients. If you want to stick to a peat, coir or ground bark is fine, but leave out the compost or garden soil. Fertilise less often with more diluted solutions. And removing any excess growth from the top, when it is still green wood.
Everybody has different growing atmospheres and different watering habits. What works for me, may not work for you, but the general idea is normally the same.
