Godly, beside cactus on photo fungous disease: "soft rot" (the scientific name I do not know, but possible find in book on cactus). The particularities this rotted: -very quick spreading on cactus, possibility of the poisoning the nearby plants through direct contact, through insect or ground. Save the cactus possible only having deleted all struck part with heavy stocks (if cactus it is enough big). - All this is written in book. Possible cure the system fungicide - I not litter (better somewhere hear).
But in practice chance there is: it is necessary all cactuses to take out of this suspicious ground (in its composition too much organic materials) and simply put vertically (for instance in thimble) in DRY place with light. The Temperature now already needs 18-25'C (since they are weakened). The First 2-3 weeks not to sprinkle. Afterwards - upon their condition.
I seem that reasons of the disease in this:
- A Cactuses were planted WITHOUT ROOTS (this so?)
- Ground was humid (?)
- An Air in terrarium too was humid and still.
Here is what multiply the cactuses a length (is described in any book):
- A blade of the sharp knife to wipe in alcohol.
- Do the cut. Advisable immediately sprinkle its ground charcoal or powdered yellow sulfur (I did not sprinkle never nothing).
- Once again wipe the blade (before the following cut).
- Cut parts of the cactus to place for 2-3 days that place of the cut to dry.
- Then bolt their vertically (put in thimble etc.). Better that lower part of cactus was in the dark (so easier get root).
- Leave in such position until from below do not appear the small white rootlet by length 1-5mm.
- Thrust CAREFULLY cactus in ground in pot and NOT to WATER.
- In week possible to begin daily sprinkle cactus.
- Through 2-3 weeks possible to begin to water water.
- Dissolved fertilizer contributes only summer, during active growing of the cactus and only when it get well the condition.
- Once in 2-4 years transplant in new ground.
- Ground for these type cactus must have little organic materials (look as land with sand, rather then as timber blackening nourishing ground).
- It is necessary constantly to search for more new information and new books...
But no worry. We whole only on way of acquisition of the experience!
In what condition your rest cactuses? They had some root before boarding in the soil?