Aligning checkbox elements in many coumns in a Shiny app

So, I wrote a Shiny app showing some checkboxes and radio buttons. For saving screen space I want to organize the checkbox answers in 2 columns. I have followed the advices given here and arrived to an acceptable interface:

But as you can see, the first column is vertically displaced (I have used label=NULL).Is there any way to have both columns vertically aligned when there's no label?

The relevant piece of code:

shinyUI(
navbarPage("navbar",
tabPanel(strong("Buscador"),value="panel2",
tags$head(tags$style(HTML(".multicol{font-size:12px;
height:auto;
-webkit-column-count: 2;
-moz-column-count: 2;
column-count: 2;
}"))),
fluidRow(column(4,
                   strong(p("Indexada en")),
                   tags$div(align = "left", 
                            class = "multicol",
                   checkboxGroupInput("index",
                                      label=NULL,
                                      choices = list("PubMed©" = 3,
                                                     "Embase©" = 4,
                                                     "CINAHL©" = 5,
                                                     "Cuiden©" = 6,
                                                     "Scopus©" = 7,
                                                     "BVS-Lilacs©" = 8))
                   )))))

Thanks in advance